The present invention relates to illumination devices using optical waveguide and, more particularly, to lighting devices for the simulation of neon lighting using optical waveguides and high intensity low voltage light sources and ideally adapted for signage and advertising uses.
Neon lighting which is produced by the electrical stimulation of the electrons in the low pressure neon gas filled glass tube has been a main stay in advertising and for outlining channel letters and building structures for many years. A characteristic of neon lighting is that the tubing encompassing the gas has an even glow over its entire length irrespective of the viewing angle. This characteristic makes neon lighting adaptable for many advertising applications including script writing and designs because the glass tubing can be fabricated into curved and twisted configurations simulating script writing and intricate designs. The even glow of neon lighting being typically devoid of hot spots allows for advertising without visual and unsightly distractions. Thus, any illumination device that is developed to duplicate the effects of neon lighting must also have even light distribution over its length and about its circumference. Equally important, such lighting devices must have a brightness that is at least comparable to neon lighting. Further, since neon lighting is a well established industry, a competitive lighting device must be light in weight and have superior xe2x80x9chandleabilityxe2x80x9d characteristics in order to make inroads into the neon lighting market. Neon lighting is recognized as being fragile in nature. Because of the fragility and heavy weight primarily due to its supporting infrastructure and power supply components, neon lighting is expensive to package and ship. Moreover, it is extremely awkward to initial handle, install, and/or replace. Any lighting device that can provide those previously enumerated positive characteristics of neon lighting while minimizing its size, weight, and handleability shortcomings will provide for a significant advance in the lighting technology.
Finally, from an environmental standpoint, neon gas has a naturally red light characteristic and thus requires the addition of various materials such as argon, mercury and phosphors to produce the varied colors required by the neon lighting industry. The fabrication of certain neon lighting clearly is burdened environmentally from having to handle some of the materials such as mercury for example.
U.S. Pat. No. 4,891,896 issued on Jan. 9, 1990 to Boren and assigned to the Gulf Development Company is an example of many attempts to duplicate neon lighting. Like this attempt, most prior art neon simulations have resulted in structures difficult to fabricate and providing a little in the way of weight and handling benefits. The Boren patent exemplifies this by providing a plastic panel with essentially bas-relief lettering. The material comprising the lettering is transparent and coated with a translucent material. The surrounding material is opaque. When the panel is back lit the lettering tends to glow with a neon-like intensity.
The more recent introduction of light weight and breakage resistant point light sources as exemplified by high intensity light emitting diodes have shown great promise to those interested in illumination devices that may simulate neon lighting and have stimulated much effort in that direction. However, the twin attributes of neon lighting, uniformity and brightness, have proven to be difficult obstacles to hurdle as such attempts to simulate neon lighting have largely been stymied by the tradeoffs between light distribution to promote the uniformity and brightness. For example, U.S. Pat. No. 4,976,057 issued Dec. 11, 1990 to Bianchi describes a device that includes a transparent or translucent hollow plastic tubing is mounted in juxtaposition to a sheet of material having light transmitting areas that are co-extensive to the tubing . The sheet is back lit by light sources such as LEDs which trace the configuration of the tubing. The tubing can be made into any shape including lettering. While the tubing may be lit by such arrangement, the light transfer efficiencies with such an arrangement is likely to result in a xe2x80x9cglowingxe2x80x9d tube having insufficient intensity to match that of neon lighting. The use of point light sources such as LEDs may provide intense light that rival or exceed neon lighting, but when arranged in arrays lack the uniformity needed and unfortunately provide alternate high and low intensity regions in the illuminated surfaces. Attempts to smooth out the light has resulted in lighting that has unacceptably low intensity levels.
It is therefore a paramount object of the present invention is to provide for an energy efficient, virtually unbreakable alternative to neon lighting that has the appearance of light around a substantial part of the circumference.
A further important object of the present invention is to provide for a lighting device that is safe to transport and economical to operate while providing all of the application virtues of neon lighting including uniformity and brightness.
Yet another object of the present invention is to provide for an alternative to neon lighting that is environmentally friendly, requiring no neon gas (or those additional materials for providing desired colors), and running on significantly less electricity that its neon equivalent.
Still another important object is to provide for a neon equivalent that is easy to install without complex electrical installations.
Yet a further object is to provide for a lighting device that can be placed in hostile environments such as in a freezer case without need for protective guards against accidental contact by customers.
These and other objects of the invention will become readily apparent and addressed through a reading of the discussion below and appended drawings.
The present invention utilizes a profiled rod of material having waveguide characteristics that preferentially scatters light entering one lateral surface (xe2x80x9clight receiving surfacexe2x80x9d) so that the resulting light intensity pattern emitted by another lateral surface of the rod (xe2x80x9clight emitting surfacexe2x80x9d) is elongated along the length of the rod. A light source extends along and is positioned adjacent the light receiving surface and spaced from the light emitting surface a distance sufficient to create an elongated light intensity pattern with a major axis along the length of the rod and a minor axis that has a width that covers substantially the entire circumferential width of the light emitting surface. More specifically and in accordance with one embodiment, the profiled rod has a substantially hemispherical section contiguous with a transparent and substantially hemispherical second section that defines a groove running the length of the second section and houses the light source. A reflecting member is juxtaposed against the external curved surface of the second section. Light emitted from the light source either directly enters or is reflected into the light receiving surface of the rod and ultimately exits through the light emitting surface. The light source is a string of point light sources spaced a distance apart sufficient to permit the mapping of the light emitted by each point light source into the rod so as to create elongated and overlapping light intensity patterns along the light emitting surface and circumferentially about the surface so that the collective light intensity pattern is perceived as being uniform over the entire light emitting surface